1. Field of the Invention
The invention relates to a liquid crystal display device and a method of fabricating the same, and more particularly to a reflection type liquid crystal display device in which an external incident light is reflected towards a viewer such that the reflected light acts as a light source, and a method of fabricating the same.
2. Description of the Related Art
As one of liquid crystal display devices, there is known a reflection type liquid crystal display device. The reflection type liquid crystal display device includes a reflection layer at which an external incident light is reflected towards a viewer, and hence, is not necessary to include a back light source unlike a transmission type liquid crystal display device which has to include a back light source as a light source.
FIG. 1 is partial cross-sectional view of a conventional reflection type liquid crystal display device.
As illustrated in FIG. 1, the reflection type liquid crystal display device 1 is comprised of a lower substrate 2, an opposing substrate 4 spaced away from and facing the lower substrate 2, and a liquid crystal layer 3 sandwiched between the lower and opposing substrates 2 and 4.
The lower substrate 2 includes an electrically insulating substrate 2a, a semiconductor device 5, a drain wiring 6, projections 7, an electrically insulating layer 8, and a reflection electrode 9. The semiconductor device 5 and drain wiring 6 are formed on the substrate 2a, and the projections 7 are formed on the substrate 2a in a pattern. The electrically insulating layer 8 covers the semiconductor device 5, the drain wiring 6 and the projections 7 therewith. The reflection electrode 9 is formed directly on the electrically insulating layer 8.
The opposing substrate 4 includes an electrically insulating substrate 4a, and a transparent electrode 4b formed on the substrate 4a and facing the liquid crystal layer 3.
The electrically insulating layer 8 is composed of organic material, inorganic material or a combination of organic and inorganic materials. The electrically insulating layer 8 formed on the drain wiring 6 acts as a passivation layer for protecting the semiconductor device 5.
The conventional reflection type liquid crystal display device 1 is accompanied with a problem as follows.
Since the drain wiring 6 is covered only with the thin electrically insulating layer 8, a light reflected at the drain wiring 6 is unavoidably yellowish in color, resulting in harmful influence to the display characteristic of the reflection type liquid crystal display device 1.
FIG. 2 illustrates how lights are reflected in the reflection type liquid crystal display device 1.
As illustrated in FIG. 2, incident lights Lia and Lib pass through the opposing substrate 4 and the liquid crystal layer 3, reach the lower substrate 2, and are reflected at the lower substrate 2. The reflected lights Lra and Lrb pass through the liquid crystal layer 3 again, and leave the opposing substrate 4.
Since the drain wiring 6 is covered only with the thin insulating layer 8 composed of metal, a space between the drain wiring 6 and the opposing substrate 4 is greater than a space between the reflection electrode 9 and the opposing substrate 4. As a result, the light Lrb reflected at the drain wiring 6 would have a greater birefringence rate (Δn×d) than that of the light Lra reflected at the reflection electrode 9, and accordingly, the reflected light Lrb would be yellowish. This causes a problem that when the liquid crystal display device displays a white image, the white image would be yellowish.
Japanese Unexamined Patent Publication No. 6-75238 has suggested a liquid crystal display device including a first transparent substrate, a second transparent substrate facing the first transparent substrate, a liquid crystal layer sandwiched between the first and second transparent substrates, a plurality of reflections electrodes formed on the first transparent substrate for reflecting an incident light having passed through the second transparent substrate, voltage-applying electrodes which apply a voltage to each of the reflection electrodes, and a light-permeable common electrode formed almost all over the second electrode. The reflection electrodes cover the first transparent substrate therewith except portions through which the reflection electrodes are connected to each other above the voltage-applying electrodes, and are formed on an electrically insulating film having a plurality of projections, only in an area in which the reflection electrodes are formed such that the reflection electrodes do not overlap the voltage-applying electrodes.
Japanese Unexamined Patent Publication No. 2001-201742 having been published on Jul. 27, 2001 has suggested a liquid crystal display device including a first transparent substrate, a transparent electrode formed on the first transparent substrate, a second substrate, an electrically insulating film formed on the second substrate and having a wavy surface, a reflection electrode formed on the electrically insulating film and having a surface reflecting the wavy surface of the electrically insulating film, and a liquid crystal layer sandwiched between the first and second substrates. The electrically insulating film is comprised of a first insulating layer having a plurality of non-uniformly arranged recessed portions defined by raised portions surrounding the recessed portions, and a second insulating layer entirely covering the first insulating layer therewith.
The above-mentioned problem remains unsolved even in the above-mentioned Publications.
It should be noted that Japanese Unexamined Patent Publication No. 2001-201742 constitutes statutory prior art to the present invention. The applicant refers to the Publication No. 2001-201742 only for the purpose of explanation of the present invention, and the reference to the Publication No. 2001-201742 does not mean that the applicant admits that the Publication No. 2001-201742 constitutes statutory prior art to the present invention.